This invention relates to log-periodic antennas, and more particularly to an improved log-periodic monopole antenna array.
U.S. Pat. No. 3,286,268 discloses a log-periodic monopole antenna with active elements spaced above a ground plane and with parasitic log-periodic elements interspersed between the active elements. The active and parasitic elements may be formed on opposite sides of a dielectric PC board by printed circuit techniques and the parasitic elements, through an integral grounding strip, are connected to ground as by soldering or the like. In applications requiring a ground plane structure made of aluminum or the like, soldering cannot be used for this purpose and instead, according to prior art practice, a two-piece aluminum ground structure clamped to opposite sides of the PC board has been employed. Fasteners such as screws extend through ground structure flanges and the PC board transversely of the latter and cause the flanges to tightly squeeze against the parasitic element strip and produce a good electrical and mechanical bond.
The above clamping practice is effective with a single monopole antenna but cannot be used in an array of such antennas in which the spacing between adjacent antennas is severely limited. This is especially true of such antennas designed to operate at microwave frequencies where the lateral spacing between adjacent antennas at the high frequency end of the array may be 6 mm or less.
This invention is directed toward a solution to this problem.